We are studying risk factors for cancers of the prostate, testis, and cervix in case-control and cohort studies. A population-based case-control study of prostate cancer was conducted in Shanghai to investigate reasons for the extremely low risk of this cancer in China. High intakes of red meat and preserved foods were associated with an increased risk, while intake of vegetables containing allium, such as garlic and onions, was associated with a decreased risk. In addition, men with a high waist-to-hip ratio, a higher density of chest and facial hair, or dry cerumen (earwax) had an elevated risk of prostate cancer, suggesting that hormones may play a role. Biochemical analyses are currently underway to evaluate the relationships of serum hormones, isoflavones, and polyphenols to prostate cancer risk. Data from a record linkage study of 100,000 men with benign prostatic hyperplasia (BPH) in Sweden gave no evidence of increased risk of prostate cancer up to 20 years after the diagnosis of BPH. In another linkage study in Sweden, we found that farmers, agriculture workers, and men employed in sedentary occupations had an excess risk of prostate cancer. These results suggest that physical activity may protect against prostate cancer and point to a need for further studies of exposures in farmers. In a record linkage study in Sweden and Denmark, patients with endometriosis had increased subsequent risk of non-Hodgkin's lymphoma, and of breast and ovarian cancer, but no increased risk for cervical or endometrial cancer. A nested case-control study in Taiwan demonstrated that infection with human papillomavirus accounted for 51% of the low-grade and 90% of the high-grade cervical neoplasia in this relatively monogamous population. Infection with Chlamydia trachomatis conferred a small independent risk of high-grade, cervical neoplasia. Human papillomavirus was measured in two laboratories by the polymerase chain reaction to amplify viral DNA in two samples of cervical cells collected 2-5 months apart from women with biopsy-proven cervical neoplasia. These measurements agreed well and confirmed the reliability of these measurement techniques.